The present invention relates to an automotive electric compressor driving apparatus comprising driving circuits for air-conditioning components, data input circuits for sensors, and a serial communication circuit for inputting driving signals and outputting sensor data.
FIGS. 4 and 5 is a partially sectional view of an automobile having a conventional electric compressor driving apparatus for an automotive air conditioner. An air conditioner controller 25 is provided in the passenger compartment 30 of the automobile. A room temperature sensor 22 for detecting room temperature and a sunshine sensor 23 for detecting sunshine are provided in the passenger compartment 30. The detection outputs from the room temperature sensor 22 and the sunshine sensor 23 are supplied to the air conditioner controller 25. A room fan driving unit 15 for driving a room fan 6 for sending cool or warm air through a duct portion 40 of the air conditioner is also provided in the passenger compartment 30, and connected to the air conditioner controller 25.
An electric compressor 1, an electric compressor driving unit 29 for driving the electric compressor 1 and a four-way valve 7 for switching the passages of refrigerant compressed by the electric compressor 1 are provided in an engine compartment 31 outside the passenger compartment 30 of the automobile. The four-way valve 7 is driven by a valve driving unit 8 in the engine compartment 31. An outside heat exchanger fan 3 is also provided in the engine compartment 31. Near the outside heat exchanger fan 3, an outside heat exchanger fan driving unit (hereinafter referred to as an outside fan driving unit) 16 is provided to drive the outside heat exchanger fan 3. At the front end of the engine compartment 31, an outside temperature sensor 21 is provided to detect outside air temperature. The electric compressor driving unit 29, the valve driving unit 8, the fan driving unit 16 and the outside temperature sensor 21 are connected to the air conditioner controller 25 by respective connection cables 35 passing through a partition wall 32. FIG. 5 is a view showing the connection of the above-mentioned conventional electric compressor driving apparatus. In FIG. 5, the electric compressor driving unit 29, the valve driving unit 8, the outside fan driving unit 16 and the outside temperature sensor 21 provided in the engine compartment 31 are connected to the air conditioner controller 25 provided in the passenger compartment 30 by the respective connection cables 35.
In the conventional automotive electric compressor driving apparatus, the electric compressor 1 is driven by a motor current having an instructed driving frequency which is instructed by a driving signal from the air conditioner controller 25. The instructed driving frequency of the driving signal is sent by an eight-bit serial signal as shown in FIG. 6A. The electric compressor driving unit 29 detects a driving frequency corresponding to an actual rotating speed of the electric compressor 1, and sends an eight-bit transmitting signal indicating the detected driving frequency to the air conditioner controller 25 as shown in FIG. 6B. This method is used because of the following reason. For the purpose of protection of the electric compressor 1, when the electric compressor 1 is not driven at a rotating speed corresponding to the instructed driving frequency, and the difference between the instructed driving frequency and the detected driving frequency exceeds a predetermined value, an occurrence of malfunction in the electric compressor 1 is determined, and operation for protection of the electric compressor 1 is performed. The air conditioner controller 25 also delivers respective driving signals to the valve driving unit 8, the outside fan driving unit 16 and the room fan driving unit 15 for driving the room fan. These driving signals are obtained by arithmetic operations using an arithmetic operation unit (not shown) in the air conditioner controller 25.
The valve driving unit 8 is provided near the four-way valve 7, and the outside fan driving unit 16 is provided near the outside heat exchanger fan 3. In other words, since these units are provided near respective connection pipes, these units are disposed outside the passenger compartment 30. Furthermore, the outside temperature sensor 21 is usually provided outside the passenger compartment 30 in order to detect outside temperature. On the other hand, the air conditioner controller 25, to which the above-mentioned units are connected, is usually disposed in the passenger compartment 30 in consideration of environmental conditions.
Therefore, the total number and the whole lengths of the cables extended between the air conditioner controller 25 and the above-mentioned units from the inside to the outside of the passenger compartment 30 are large. Furthermore, the number of connectors 38 provided at the passing-through parts of the partition wall 32 of the passenger compartment 30 is large, whereby the reliability of the electric connection is low. In particular, since the output signal from the outside temperature sensor 21 has a small analog voltage value, the output signal is susceptible to electric noise if the cable is long.
Accordingly, an object of the present invention is to provide an automotive electric compressor driving apparatus capable of reducing the number of connectors 38 for the various units and sensors for air-conditioning, and capable of enhancing the reliability of electric connection.